In a refrigeration cycle for vehicle air conditioning, as disclosed in patent literature 1 and patent literature 2, for example, there have been already known the inventions where, to enhance the operation efficiency of the refrigeration cycle, that is, aiming at the acquisition of a higher refrigerating capacity with smaller power of a compressor, a constitutional part which includes a new function is added to a predetermined air conditioning unit or a new air conditioning unit.
Out of these patent literatures, patent literature 1 discloses a heat exchanger which functions as a condenser constituting a refrigeration cycle, wherein the heat exchanger is constituted of a flat tube, corrugated fins, a first tank and a second tank. A refrigerant upstream side of a core formed of the flat tube and the corrugated fins constitutes a condensing part, a refrigerant downstream side of the core constitutes a supercooling part, and a gas/liquid separation part is arranged between the condensing part and the supercooling part. A refrigerant which is condensed by passing through the condensing part is further cooled (supercooled) thus enhancing a cooling ability of a refrigeration device. In patent literature 1, there is also described an idea where a rate at which a heat radiation area of the supercooling part occupies with respect to a heat radiation area of the whole heat exchanger is set to a value which falls within a fixed range (10% to 30% in the patent literature 1).
Further, in patent literature 2, there is described the constitution where an internal heat exchanger which performs a heat exchange between a high-pressure refrigerant flown out from a condenser and a low-pressure refrigerant flown out from an evaporator is arranged on a path of a refrigeration cycle.